Forces & MatterEdexcel GCSE Physics: Topic test

20 questions, 54 marks

Edexcel GCSE Physics

Forces & Matter topic test

Total 54 marks

Name

Class

Date

1
A set of bathroom scales contains a spring beneath the platform. When a person stands on the scales, their weight compresses the spring, and the scales use the amount of compression to calculate and display the person's weight. The spring has a spring constant of 5000 N/m and behaves elastically for any compression the scales are designed to measure.
(a)
What does it mean to describe the spring's compression as 'elastic' in this range?
[1 mark]
AThe spring returns to its original length once the force is removed
BThe spring becomes permanently shorter every time it is compressed
CThe spring's material changes colour when compressed
DThe spring conducts electricity better when compressed
(b)
A person weighing 700 N stands on the scales. Using F = k × e, what compression does this produce in the spring?
[1 mark]
A3571 m
B0.14 m
C5700 m
D0.0014 m
(c)
Explain how the manufacturer could redesign the spring so the scales can safely measure people up to 1500 N without the spring being compressed beyond its elastic limit.
[2 marks]
Total for question 1: 4 marks
2
A farmer wants to reduce the damage his tractor causes to wet, soft soil. He replaces the tractor's standard wheels, which have a small contact area with the ground, with much wider, low-pressure tyres, without changing the tractor's total weight.
(a)
How does fitting much wider tyres reduce the pressure the tractor exerts on the soil, given that its weight is unchanged?
[1 mark]
AWider tyres reduce the tractor's total weight
BWider tyres increase the force pushing down on the soil
CSince pressure = force/area, spreading the same force over a larger contact area produces a lower pressure
DWider tyres prevent any force at all being transmitted to the soil
(b)
The tractor weighs 45 000 N. With the wide tyres fitted, its total contact area with the ground is 1.50 m². What pressure does the tractor now exert on the soil?
[1 mark]
A150 000 Pa
B67 500 Pa
C3 000 Pa
D30 000 Pa
(c)
Explain why reducing the pressure the tractor exerts on the ground in this way reduces the risk of it sinking into soft soil.
[2 marks]
Total for question 2: 4 marks
3
Engineers designing a new reservoir dam need to know how water pressure varies with depth against the dam wall, to ensure the wall is thick enough at the bottom, where pressure is greatest. At a depth of 25 m below the water surface, the density of the reservoir water is 1000 kg/m³.
(a)
Calculate the pressure difference due to the water alone at a depth of 25 m below the reservoir's surface.
[3 marks]
(b)
Explain why the dam wall needs to be built much thicker at its base than near the top of the reservoir.
[4 marks]
Total for question 3: 7 marks
4
A toy company is designing a spring-loaded launcher for a small foam rocket. The launcher's spring has a spring constant of 250 N/m and obeys Hooke's law up to a maximum compression of 0.20 m, beyond which the spring would be permanently damaged.
(a)
Calculate the maximum elastic potential energy that can be stored in the spring without damaging it, and explain what happens to this stored energy when the spring is released to launch the rocket.
[6 marks]
(b)
Explain why compressing the spring beyond its limit of proportionality (elastic limit) would permanently damage it, and explain why, for a compression that goes just past this limit, the work done compressing the spring would be greater than the elastic potential energy it could then release.
[6 marks]
Total for question 4: 12 marks
5
An engineer is testing a bungee cord for a fairground ride before it is used with a rider. She hangs increasing loads from the cord and measures its extension each time, checking that the extension stays proportional to the load within the safe working range.
(a)
What is meant by the bungee cord's distortion being 'elastic' within this proportional range?
[1 mark]
AThe cord becomes permanently longer no matter how small the load
BThe cord returns fully to its original length once the load is removed
CThe cord snaps as soon as any load is applied
DThe cord's spring constant increases every time a load is added
(b)
A load of 900 N produces an extension of 0.60 m within this proportional range. Using F = k × e, what is the cord's spring constant?
[1 mark]
A1500 N/m
B540 N/m
C0.00067 N/m
D15 N/m
(c)
Explain what would happen to the cord's behaviour if a rider's weight caused it to be stretched beyond its elastic limit, and why this would matter for the safety of the ride.
[2 marks]
Total for question 5: 4 marks
6
A glass of water has several ice cubes floating in it, each fully surrounded by air above the water surface and partly submerged below it. Ice is less dense than liquid water.
(a)
Why does the ice cube float rather than sink to the bottom of the glass?
[1 mark]
AIce has a greater density than water, so it is pushed upward
BSurface tension alone holds the ice cube up at the surface
CThe ice cube's weight decreases as soon as it touches the water
DIce is less dense than water, so it only needs to displace a volume of water with a weight equal to its own weight while partly submerged, producing enough upthrust to balance its weight
(b)
Once the ice cube is floating in equilibrium, what is the upthrust acting on it equal to?
[1 mark]
AZero, since the ice cube is not fully submerged
BThe total weight of all the water in the glass
CThe weight of the ice cube (which equals the weight of the water it has displaced)
DThe weight of only the submerged part of the ice cube, ignoring the part above the surface
(c)
Explain, using the idea of density, why an ice cube only needs to submerge part of its volume in order to float, rather than submerging completely like a denser object would.
[2 marks]
Total for question 6: 4 marks
7
A hydraulic barber's chair uses a small pedal-operated piston with a cross-sectional area of 0.0015 m², connected by hydraulic fluid to a much larger piston, of area 0.045 m², that supports the seat and raises it when the barber presses the pedal.
(a)
A force of 120 N is applied to the small pedal piston. Calculate the pressure this creates in the hydraulic fluid.
[3 marks]
(b)
Explain, using the idea that pressure is transmitted equally through a fluid, how this pressure allows the much larger piston to lift a heavy person sitting in the chair, and calculate the force produced on the larger piston.
[4 marks]
Total for question 7: 7 marks
8
A gas cylinder is fitted with a safety pressure relief valve to stop it exploding if the internal pressure becomes dangerously high. The valve consists of a small disc of area 0.00020 m² held shut over an opening by a spring; gas pressure inside the cylinder pushes outward on the disc, while the spring pushes inward to hold the disc closed. The spring has a spring constant of 4000 N/m and is compressed by 0.03 m when holding the valve closed under normal conditions.
(a)
Using Hooke's law, calculate the force the spring exerts to hold the valve disc closed under normal conditions, and explain how the spring must be designed differently if the cylinder needed to be safely used at a much higher normal operating pressure.
[6 marks]
(b)
Explain, using the equation pressure = force/area, why the valve opens once the gas pressure inside the cylinder exceeds a certain value, and calculate the internal gas pressure at which this valve would just begin to open.
[6 marks]
Total for question 8: 12 marks

End of questions